Has our war on microbes left our immune systems prone to dysfunction?

Book review: An Epidemic of Absence takes on the worms you're missing.

An Epidemic of Absence: A New Way of Understanding Allergies and Autoimmune Diseases could be co-marketed with the Thomas Rockwell’s children’s classic How to Eat Fried Worms. It begins with the author, Moises Velasquez-Manoff, recounting his border-crossing to Tijuana to infect himself with Necator americanus—hookworms—in an attempt to cure the asthma, hay fever, food allergies, and alopecia that had plagued him since childhood. In the next three hundred pages, the author very cogently explains the idea that led him to willingly infect himself with a parasite known to cause severe diarrhea, anemia, and mental retardation in children.

Velasquez-Manoff marshals the reams of evidence researchers have accumulated to support said concept: the hygiene hypothesis, but with an updated, parasitic twist. The ideas he presents haven't been accepted by many in the medical community, and there's little high-quality evidence, in the form of well controlled trials, that exposure to parasites could have positive effects on human health. So, even if the author is thorough, it's important to keep in mind that the evidence he's presenting is primarily in the form of correlations.

Vanishing microbes, a rising tide of allergies

Since children's author Rockwell penned that first worm eating guide in 1973, the incidence of allergies and autoimmune diseases—both disorders in which the immune system attacks things that it should know are harmless—have skyrocketed in the developed world. Those who read that book as children have watched it happen; whereas a PB&J was the standard brown bag lunch for us, our children’s schools are now all nut free.

Adherents of the paleo diet maintain that the trouble started with the advent of agriculture in the Neolithic Revolution, about 12,000 years ago, and has been getting progressively worse. They argue that humans have adapted to eat only foods that could be hunted or gathered, and the recent preponderance of allergies demonstrates that we have not yet evolved to eat food that must be cultivated, like wheat and legumes.

Velasquez-Manoff cites examples of contemporary hunter-gatherer societies whose members are, in fact, much healthier than their age-matched counterparts in the developed world. Yet evolutionary geneticists have an alternate explanation for the dramatic upswing in immune disorders. Genes that cause disease but are common throughout a population, the thinking goes, must confer some benefit or they would have been selected against. And the genetic variants that predispose modern humans to immune disorders are distressingly common. They are also found in genes that are present across a wide variety of species, indicating that they are quite ancient—further evidence that they probably have an important function. Research on different immune diseases all over the world suggests that these genes are involved in defense against pathogens.

For almost all of our evolutionary development humans were pretty much covered in bacteria, viruses, and parasitic worms. Velasquez-Manoff refers to this group as "old friends." These are different from the disease-causing bugs we vaccinate against; we got those much later in our evolutionary development, from the animals we domesticated, and Velasquez-Manoff is clear in his insistence that vaccinating against them is necessary and good.

But finding a way to achieve some sort of truce with "old friends" was the immune system’s essential and constant job throughout our co-evolution. It is only after the sanitary reforms of the early nineteenth century that we suddenly find ourselves in an environment relatively purged of microbes, and these protective genes may be a liability in that environment, rather than an asset.

The Hygiene Hypothesis

A simplistic view of the hygiene hypothesis is that in the absence of something dangerous to fight against—the cholera toxin, for example—immune cells get confused, or bored, and fight against harmless stimuli like dust mites and peanuts instead. But there is a more nuanced view. Our immune systems co-evolved with an enormous community of microbes, and were in fact shaped by them. Many became established, long-term, and vital residents in our guts; the importance, and in fact the very existence, of these commensals has only recently been realized.

Constant exposure to all of these bugs, as a unit, enhanced the regulatory arm of the immune system, modulating responses so that we could tolerate the filthy environment in which we lived while at the same time (hopefully) fighting off those pathogens that posed a mortal threat and not destroying our own bodies in that process. In the martial analogy that is inevitable in discussing immunology, ancient human immune cells that were always surrounded by microbes were like battle-hardened old soldiers who have learned the ability to watch warily when encountering something new, waiting to see whether or not it is dangerous; modern immune cells raised in our hyper-sanitized environment are like new recruits just given their first gun, testy and jumpy at the first hint of a threat and liable to blow up their surroundings in inappropriately directed and outsized force. Experience has not taught them moderation.

On the molecular level, immune cells in the dirty old days made more anti-inflammatory signaling molecules; now, our cells make predominantly pro-inflammatory signals.

Autoimmune diseases are currently thought to arise from an interplay of genetic and environmental factors, notably stress. Some have argued that this means genes are everything, because what modern human doesn’t have stress in his life? Only those genetically primed go on to develop disease.

But Velasquez-Manoff takes us to Sardinia to upend this argument. Sardinians are an isolated, inbred group, and they have experienced a twin epidemic of multiple sclerosis and type I diabetes, both autoimmune diseases, in the past sixty years—ever since they got rid of malaria. For the past few thousand years, those Sardinians that were genetically resistant to the malaria parasite survived; those that were not did not. The relentless presence of malaria in their environment shaped their genomes.

And then when malaria was suddenly removed, its lack may have allowed the immune system’s underlying protective feature to go into overdrive. A similar, if less dramatic, trajectory of events could explain how the removal of most of our "old friends," but especially the worms, uncovered underlying genetic tendencies that only yield autoimmune and allergic disorders in our modern context.

The Helicobacter pylori story further underscores the importance of context. H. pylori definitely, without a doubt, causes ulcers. And stomach cancer. Yet it protects against heartburn, esophageal cancer, asthma, and eczema.

H. pylori has been with humanity since before we left Africa. Why would it make only some people who harbor it sick, and why so much more so in the last few hundred years? Our increased life expectancy doesn’t account for it. In days of yore, when humans routinely encountered H. pylori early in childhood, the bug taught their immune cells tolerance and protected against asthma. Now, since we grow up in cleaner environments, we encounter it later. Not only does its early absence predispose to asthma, its late introduction induces ulcers. But the effects of H. pylori infection are dictated not only by when it is introduced to the human gut, but by the other microbes it does or does not encounter there.

Parasitic worms also seem to be significant regulators of the immune system, able to elicit just the right balance of ferocity and temperance. Deworming campaigns the world over are promptly and predictably followed by increases in asthma and allergy, and the degree of allergy in a society is inversely proportional to how wormy and dirty it is. Hence, people suffering from allergies and autoimmune diseases are now infecting themselves with hookworms, which—on an anecdotal level at least—has alleviated maladies ranging from MS to autism to celiac disease.

Seeing worms everywhere

Yes, he includes autism in the list of modern diseases caused by our out-of-whack immune systems. Along with other cases where immune dysfunction hasn't been established, like obesity, cardiovascular disease, type 2 diabetes, and cancer.

There are some serious problems with blaming all of these on immune dysfunction, but we'll focus on a single example: autism. Just as the absence of worms’ mediating effects on our immune system causes some people to have an allergic response to harmless ingested proteins and others to attack their own tissues, the argument goes, chronic inflammation in the womb generates fetuses with autism.

Velasquez-Manoff cites circumstantial evidence supporting this idea—autism follows the same demographics as asthma, occurring primarily in firstborns, males, and urban centers in wealthy countries, and one of the risk factors for autism is a mother with an autoimmune disease. But this demographic data is obtained by questionnaire, often with quite a small sample size, and is thus inherently suspect.

As researchers continue to delve into the cause of autism, the data they are accumulating indicates that it is a genetic and not an immune disease. Environmental factors are almost certainly involved, and it is a complex genetic disease—mutations in many different genes, possibly hundreds of them, can cause it. Most cases of autism are sporadic, meaning that only one individual in a family is affected.

But rigorous experiments have shown that even sporadic cases can generally be traced back to spontaneous genetic mutations in the developing fetus. The mutated genes are involved in forming and maintaining the gross architecture of the brain, lending credence to the idea that autism and its accompanying spectrum of disorders arises from a lack of connectivity among neurons. Few of the mutated genes associated with autism seem to be involved in immunity.

When we discussed his book, Velasquez-Manoff did suggest there were limits to how well we should treat our old friends. Deworming campaigns, he said, are still necessary, since the world's poor children are the ones who bear the brunt of the worms' negative effects. Their parasites exacerbate their malnutrition and cause them to miss a lot of school, promoting a cycle of poverty.

The sanitary reforms of the mid-nineteenth century, along with the germ theory of disease and the vaccines and antibiotics it precipitated, were undoubtedly an enormous medical coup that largely eliminated the infectious diseases that had formerly killed a quarter of the population by age one. We no longer live in fear of the Black Death or similar medieval scourges that killed millions.

But along with these breakthroughs came the idea that all microbes are all bad, which yielded needlessly antibiotic soap and sanitary covers for toddlers sitting in shopping carts. The backlash, that we need to get to know and love the microbiota inhabiting our guts, is yielding Brooklyn hipsters who brew their own kombucha and the very unfortunate anti-vaccine movement. This book argues that microbes are neither good nor bad, but can be either or both depending on the context in which we encounter them. And the real cause of the allergy and autoimmune epidemic is that we have severely screwed up that context, both inside our guts and outside in the rest of the environment.

These ideas are still well outside the medical mainstream and, in several cases, the authors intense focus on immune disorders had led him to get carried away. But Velasquez-Manoff has put together a well argued case that, for at least some disorders, our interactions with microbes should at least be given serious consideration. And, despite the copious research involved, the book remains very readable.

And since you were wondering: the worms seemed to clear up his sinuses and skin, but he didn’t grow hair. And they gave him terrible, terrible diarrhea.

102 Reader Comments

There's a story floating around about a man who used Whipworms to treat ulcerative colitis. It appears that as the worms gnaw on the walls of his intestine/colon, it causes an increased production of mucus in those areas, which helped to alleviate his symptoms.

I've often thought that asthma and allergies seem more common now, but being rather young I don't have much to compare it to first-hand - only my grandfather accusing my generation of faking asthma to get out of work.

Even if it's all true, however, I'd take my asthma and assortment of minor allergies any day over *widespread plague killing people off.*

I'm glad people do not dismiss the theory that your immune system needs something to fight to stay at "DefCon 2". My family has been saying something similar for my entire life plus a few generations, usually "what doesn't kill you only makes you stronger". As a family, we each get typically get 1 cold or flu illness every 2 years and maybe a medium disease once in our lives. It might be good mix of genes, but our bodies seem in good working order to not have allergies or other autoimmune disorders. I was raised to just tough out a cold as our immune systems are way better at fighting illness than any medicine on the market. I firmly think that our immune systems need practice at fighting the occasional bug to stay in fighting shape for the really big diseases and stave off immune boredom.

While all of this stuff seems plausible and perhaps an area to pursue, it is in desperate need of a large(ish) sample group and some peer review!

The plausibility really cannot be denied. After all, what are those vaccinations we get as children? Weakened strands of the diseases they prevent. Exposure to these kinds of pathogens, or any kind of pathogens, is what builds the immune system. It's kind of like expecting your antivirus program on your computer to keep you protected without updating the virus definitions.

While all of this stuff seems plausible and perhaps an area to pursue, it is in desperate need of a large(ish) sample group and some peer review!

The plausibility really cannot be denied. After all, what are those vaccinations we get as children? Weakened strands of the diseases they prevent. Exposure to these kinds of pathogens, or any kind of pathogens, is what builds the immune system. It's kind of like expecting your antivirus program on your computer to keep you protected without updating the virus definitions.

Not really the same thing. The idea behind this is that an idle immune system tends to cause more auto-immune disorders, not that it lets in more legitimate infections than usual.

allergies *are* far more common in developed countries than those that are not. There are a lot of people I know who've moved to the US and whose children have loads of allergies (horribly restricted) while the nephews and neices who stayed behind don't.

Now it worries me as well that he

Quote:

cites circumstantial evidence supporting this idea—autism follows the same demographics as asthma, occurring primarily in firstborns, males, and urban centers in wealthy countries, and one of the risk factors for autism is a mother with an autoimmune disease.

In the right (wrong) hands that quote could lead to some ugliness. Wish people would steer clear of putting down claims that need to be researched more thoroughly; still, controversy does sell.

Nice work pointing that one out! Will try and get a copy none the less.

I rarely go to the doctor for anything that isn't debilitating (and the rest of the time is when it's mandated for some reason, like required inoculations for school). I also rarely get sick. There's not religious reasons, my family just doesn't elect to go to the doctor much; once we get older we go considerably more often, as heart problems and the like become far more likely.

I'm 32, and had my second (noticeable) flu the day before yesterday. I started feeling ill with a slight fever after work, fever was nasty until about 0500 with a headache and muscular soreness, by 0900 yesterday my temperature was back to normal. This is a pretty common pattern; everyone around me is getting ill, I might get a touch of fever. Maybe. The November before last I puked for the first time in at least 26 years (I remembered I was a child, but my parents couldn't remember if I was 4 or 6).

The pattern is the same across my family. We go in for important stuff (broken bones, major cuts, and when we start getting old enough that shit just wears out), and we're markedly healthier than pretty much everyone else. Longer-lived, longer active lives, less illness.

It could be a genetic factor, but it's spread broadly enough across the family (and we use the term inclusively; I have quite a few people that we consider close family members that aren't genetically close at all anymore) that I tend to think it's a lifestyle factor.

I would say that the family helps; we're very close, and we have a lot of family history. Together, it seems like we have a much different view on things than most people because we always have a safety net of sorts, and we have a lot of previous generations to look back on and see what they dealt with, and how they did it.

As a foreigner, something that astounds me about Americans is how afraid they are of germs.

Everything from toilet seat covers and anti-bacterial products to OCD behaviors such as using your elbows to turn off the faucet after you're done washing your hands is indicative of a culture where germs are the devil and must be avoided at all costs. The result? People's immune systems are not only weak, but also completely out of whack. People get sick way too often and it seems like every other person has either some sort of allergy or asthma.

As an "American," something that astounds me about Americans is how a third to a half don't bother to wash their hands at all after using a toilet/urinal. Guess not all of 'em are afraid! (Sample size admittedly rather low, male-exclusive.)

Is it possible (forgive my being non-PC here), that we have "evolved" into a demographic where weaker genes survive, and where people with allegies, autoimmune diseases, etc. would otherwise either not survive or reproduce, but can and do now?

Also, this notion has been tossed around before, but does how much does the ability to diagnose these problems correlate to the increased numbers now claimed?

Lastly, it has been well known that returning astronauts have compromised immune systems. No conclusive cause has been determined; some have taken to studying cells in low-G thinking that might be the cause (http://www.newscientist.com/article/dn8 ... ystem.html). Perhaps, it is just because they live in a sterile environment, even if just for a few days, such that their immune systems become "complacent".

There's a story floating around about a man who used Whipworms to treat ulcerative colitis. It appears that as the worms gnaw on the walls of his intestine/colon, it causes an increased production of mucus in those areas, which helped to alleviate his symptoms.

Not only that, the FDA has slowly been approving clinical trials with those pig worm eggs (e.g. Trichuris suis) for those with any Inflammatory Bowel Disease (IBD) which includes Chron's and Ulcerative colitis.

enraged_camel wrote:

As a foreigner, something that astounds me about Americans is how afraid they are of germs.

Everything from toilet seat covers and anti-bacterial products to OCD behaviors such as using your elbows to turn off the faucet after you're done washing your hands is indicative of a culture where germs are the devil and must be avoided at all costs. The result? People's immune systems are not only weak, but also completely out of whack. People get sick way too often and it seems like every other person has either some sort of allergy or asthma.

In my opinion, I don't see it as an American phenomena, but more of a media hysteria type thing. Example, I read a few years ago an article by this uninformed person that she read that Clostridium botulinum can be found in soil. Her opinion, try to limit your kids playtime in playgrounds/sandboxes/soil and use hand sanitizers. Seriously, WHAT THE HELL!?! First of all, most organisms (good and bad) are found in the soil. Secondly, clostridium is a spore. Regular alcohol found in hand sanitizers has no effect on spores.

This is why I see people going crazy with anti-microbial soaps/gels and being overly too cautious when their kids go out to play. When I was growing up, we spent most of the time playing outside getting dirty and scraped up. Parents these days either want to shelter their kids or are to lazy to take them outside to play. They'd rather see them in the game room with the Xbox being all safe from germs.

Adherents of the paleo diet maintain that the trouble started with the advent of agriculture in the Neolithic Revolution, about 12,000 years ago, and has been getting progressively worse. They argue that humans have adapted to eat only foods that could be hunted or gathered, and the recent preponderance of allergies demonstrates that we have not yet evolved to eat food that must be cultivated, like wheat and legumes.

That's just BS. It's more likely that medicine has become good enough people with defective genes not only survive but also thrive.

I live in a third world country and had caught all sorts of parasitic diseases (including bot fly larvae) and guess what? I STILL HAVE THE SAME ALLERGIES AS I HAD SINCE I WAS A KID. In fact I'm becoming more sensitive to cinnamon instead.

Velasquez-Manoff cites examples of contemporary hunter-gatherer societies whose members are, ...in fact, much healthier than their age-matched counterparts in the developed world.

pre-selected by virtue of having survived an infant mortality rate two orders of magnitude higher than seen in developed nations.Infant mortality among the Khoisan: 200-300/1000Infant mortality in Singapore: 2.31-2.60/1000

Deaths from Scarlet Fever in USA:1850s: up to 250/100,0001960: almost 0Several factors caused the big drop from the 1880s onwards, most notably hygiene and milk pasteurisation. Antibiotics only arrived on the scene in the 1950s, at which point Scarlet Fever was already a negligible threat.

I could go on, at length.

The ideas presented here aren't exactly new, and have been floating around for decades. There is interesting evidence for an association between certain parasites and auto-immune diseases, but in almost all cases the morbidity reliably induced by the parasite exceeds the immune benefit that might be conferred. And, of course, anyone with an intestinal worm represents an infection risk for others unless they practise the most scrupulous cleanliness.

There's a lot to be said for the idea that our bodies have evolved to be part of an ecosystem, interacting with multiple microbial species. But those who propound this stuff tend to gloss lightly over the fact that this evolutionary trajectory also involved a large number of deaths at an early age. The fittest survived the mass winnowings of infancy and childhood, and were generally pretty healthy, but they left behind a mass of bodies.

We have set ourselves at odds with evolution. We have decided that all life is precious, not just that which can survive a barrage of microbial assaults. If that means we need to develop a more sophisticated (and artificial) way of regulating our immune system then so be it.

My thoughts are we need to have children go back to eating dirt. There is far too much oversight of children these days, driving too and from school...etc, but that is another topic. Babies like to put everything in their mouths...let them, they are doing it for a reason.

Another thing is our anxieties are very bad. Anxieties are our bodies way of making us do things when we need to do them, but in todays society there is much that we can do little about and our "do something" anxieties cause problems with our whole system, that needs to be mitigated by practices that lower the anxieties of the people. To understand what their bodies are doing and why and tools to rationalize to lower anxieties.

No doubt this contains some truth, but even more likely it's a part of a wide range of influences. But what's really interesting is that there does appear to be a significant divide between city and country living that might give us some hints.

Asthma is more likely in urban areas where there is a greater focus on hygiene and there's a lot more pollution from cars and factories. People in the country seem more inclined to eat all manner of agricultural produce, whereas people in the city have greater access to fast foods.

People in the country are more likely to be outside in the sun making some Vitamin D and doing physical labor while people in the city are likely to be locked away in buildings and remain seated all day. Country kids play outdoors on dirt, trees and rivers while city kids seem to live in front of the tv or computer.

In the country people are more likely to sync with the natural clock that is the sun. In the city, artificial lights mean that people are forcing sleeping routines that humans are yet to adapt to.

There's probably no one cause to these issues. I think the days of a Silver Bullet are gone and we need to look at issues like this from as many different angles as we can. Otherwise the narrow perspective would have us lurching from one potentially dangerous fad to another.

I'm glad people do not dismiss the theory that your immune system needs something to fight to stay at "DefCon 2". My family has been saying something similar for my entire life plus a few generations, usually "what doesn't kill you only makes you stronger". As a family, we each get typically get 1 cold or flu illness every 2 years and maybe a medium disease once in our lives. It might be good mix of genes, but our bodies seem in good working order to not have allergies or other autoimmune disorders. I was raised to just tough out a cold as our immune systems are way better at fighting illness than any medicine on the market. I firmly think that our immune systems need practice at fighting the occasional bug to stay in fighting shape for the really big diseases and stave off immune boredom.

What does "just toughing out a a cold" have to do with it? Nobody is claiming that taking symptomatic OTC meds for minor illnesses is what is causing people to have allergies.

Boskone wrote:

I would believe it.

I rarely go to the doctor for anything that isn't debilitating (and the rest of the time is when it's mandated for some reason, like required inoculations for school). I also rarely get sick. There's not religious reasons, my family just doesn't elect to go to the doctor much; once we get older we go considerably more often, as heart problems and the like become far more likely.

I'm 32, and had my second (noticeable) flu the day before yesterday. I started feeling ill with a slight fever after work, fever was nasty until about 0500 with a headache and muscular soreness, by 0900 yesterday my temperature was back to normal. This is a pretty common pattern; everyone around me is getting ill, I might get a touch of fever. Maybe. The November before last I puked for the first time in at least 26 years (I remembered I was a child, but my parents couldn't remember if I was 4 or 6).

The pattern is the same across my family. We go in for important stuff (broken bones, major cuts, and when we start getting old enough that shit just wears out), and we're markedly healthier than pretty much everyone else. Longer-lived, longer active lives, less illness.

Again, nobody is saying that going to the doctor for minor things is what's causing allergies. More activity probably helps, but now that's *completely* off topic from the article.

The general idea that more parasitic infections might prevent allergies certainly seems plausible, but I hate how it brings out all this "I don't get sick because I was raised right" sentiment that is only tangentially related to the actual science at best. We all have a natural tendency to look at the suffering of others and then immediately jump to finding some reason why the same tragedies couldn't possibly befall us. Autism, allergies, and autoimmunity are great at evoking this because we don't have good explanations for them.

How about all those chemicals we are surrounded with such as Bisphenol A, phtalates and other chemicals used as solvents in plastic materials that we nowadays have everywhere?

Also has anyone even considered all these pesticides that are being used in food. New variants ought to have been developed and taken in use during the past few decades, especially when they had to stop using DDT. Maybe in developing countries people cannot afford pesticides for their crops which could explain why they are less prone to autoimmune diseases. The same reasoning can be made with the plastics above although I believe that people in the developing world are getting more and more exposed to such chemicals, lately.

Has anyone examined the correlation between vaccination and autoimmune responses? A vaccine is certainly playing with our immune system and I'm surprised that I cannot find studies that have thoroughly investigated this.

It is quite evident that the standard of the animals that farmers graze for production of meat and milk products have declined. They are pumped with hormones, live in more restricted environments and antibiotics are used frequently to battle the diseases and infections those animals develop because they don't cope well with the surroundings. All of this to optimize profit margins.I talked to a farmer a while back and he said that back in the '70s all that was found in the medicine closet was a jar of ointment which was used on the animals when they got injured from the barb wire on the fences. Today its full of a large diversity of pills and ampoules. This meat be it pork, beef or poultry we eat everyday and I really wonder how good this meat really is. The last _known_ series of incidents are the Creutzfeldt-Jacob disease in man and the mad cow disease in foe that turned out to be caused by a strain of badly folded proteins; the prions. These proteins arose because the animal feed contained meat and bone marrow from other animals so cattle that are designed to eat grass were basically forced into cannibalism. I'm quite sure that we can blame the grazing industry for the development of antibiotic resistant bacteria and I wouldn't be surprised if it turned out that the meat from those animals at least contribute to the development of auto-immune diseases.

As a kid, I can't remember a single case of peanut allergy and nearly everyone had peanut butter and jelly sandwiches for lunch at school. There is definitely something going on here.

I'm no scientist, but sometimes authors of these sort of books seem to ignore certain facts. Like for instance. the Paleolithic diet. It's proponents never mention the fact that the average life span of the paleolithic human was about 40 years! My aunt practically ate rice and beans her whole life and died at 103. Her husband died at 106! And they were both heavy legume and grain eaters.

In any case, I think there is something in the fact that we are too germ crazy these days. But George Carlin warned us about that a long time ago.

Humanity has survived perfectly since, well, the beginning of humanity, while surrounded by all kinds of germs and disease.

God I hate this fucking argument. Life expectancy has more than doubled in the past century. If you think we're worse off now than "since the beginning of humanity" then you're welcome to kill yourself at 30.

Humanity has survived perfectly since, well, the beginning of humanity, while surrounded by all kinds of germs and disease.

God I hate this fucking argument. Life expectancy has more than doubled in the past century. If you think we're worse off now than "since the beginning of humanity" then you're welcome to kill yourself at 30.

The 30 years argument is only valid if you take into account high infant mortality. Otherwise after 60's was very common. The 50% infant mortality rates were common and stupidly included for stats and cause a dramatic view that it is so much better now.

I'd take worms over industrial dermatitis or bad asthma or bad hay fever any day.(I don't have asthma or bad hay fever)

I'd happily take the worms over having my lactose intolerance.

iamaelephant life expectancy increased dramatically over the past 100 years but not very much (in western countries) in the last 30 - 50 years which is when the disinfect/sanitize everything mentality kicked in.

In my opinion, I don't see it as an American phenomena, but more of a media hysteria type thing. Example, I read a few years ago an article by this uninformed person that she read that Clostridium botulinum can be found in soil. Her opinion, try to limit your kids playtime in playgrounds/sandboxes/soil and use hand sanitizers. Seriously, WHAT THE HELL!?! First of all, most organisms (good and bad) are found in the soil. Secondly, clostridium is a spore. Regular alcohol found in hand sanitizers has no effect on spores.

This is why I see people going crazy with anti-microbial soaps/gels and being overly too cautious when their kids go out to play. When I was growing up, we spent most of the time playing outside getting dirty and scraped up. Parents these days either want to shelter their kids or are to lazy to take them outside to play. They'd rather see them in the game room with the Xbox being all safe from germs.

This brings up another point about our own personal gut and skin fauna; the neutral or beneficial organisms can keep the harmful ones in check by their mere presence and competition for resources. But using indiscriminate antibiotics or sanitizers can wipe them out and make them start all over again with the harmful kind on an even footing.

You can rest assured that if I ever have kids and the school says they each need to bring tissues and handsanitizer to class I'll tell them to bugger off.

It's ridiculous how people seem to think coating themselves with that shit will work against the common cold.

I can understand and agree with the hand sanitizer, but what do you have against tissues? If someone has a runny nose, is it supposed to help their overall health to wipe it on their shirt tail instead? Or should you just wipe it on your hand, and then smear the snot around on everything?

If you wipe your nose with your hand and then offer to shake mine, I won't want to do it, but not because I'm some sort of germ paranoid. It's just because I don't want snot on my hand.

Chemicals i do not believe after all in General this was MUCH worse in the 70s and 80s. (Still remember the predictions of all rivers and forests being dead soon, when I was yonger, stronger environmental standards did wonders to solve that in the industrialized countries. Hell you can swim in most rivers that would have eaten you live 20 years ago.)

But I second the comment that life expectancy is increasing so I would be very careful to talk about worse health today. And yes it is increasing more slowly now but that seems to be because we hit some natural borders, all the low haning fruits have been taken. Also it still is increasing fast enough if you look at our pension problems.

In the end the dirt hypothesis makes the most sense, although I woldn,t infect myself with worms for that. Defitely some studies are needed. One thing we could do is to limit antibacterial cleaning outside of hospitals.As far as I know there is literally no scientist who says they are a good idea or better for health.

Wow, this comment thread is a cesspit of personal anecdotes. It's rare to see one this bad on Ars.

It's not surprising. This is a subject that invokes a lot of personal stories because of the way it affects us.

It is generally accepted that, whatever the cause, allergies and auto-immune problems tend to be controlled by what happened as a child (not always, but enough), so people think about their own childhood. Many people are also parents and think about how they are raising their children. Even people that aren't parents but have plans to be (like myself) are going to think about how they would deal with this situation.

For my own personal anecdote, I'd say that there is some truth to this idea. I'm very healthy, at least from the point of view of my immune system. I have now gotten to the point where I can predict when I get ill (cold-like symptoms for a week in spring and autumn). I have all sorts of other issues that require me to go to the hospital, but it isn't infections. The childhood portion of this is that my mother didn't put that much effort in to sterilizing the environment that we lived in. It was mostly clean, but my mum was busy, so vacuuming would be done every 1-2 weeks, the kitchen was kept tidy, but rarely fully cleaned etc. etc. I grew up being surrounded by slight mess.

The secondary point is one of my mum's friends. She is very clean, I mean really clean, she cleaned our house whenever she came over. She has a daughter, and my mum says that she is the sickest child she has ever known. Constantly ill, plagued by allergies, my mum puts it down to her friend being so clean.

It is anecdotal, so these may be completely false. I might be missing something important. I'm putting this out there as my opinion. Which is fine, since the Ars comments aren't a peer-reviewed journal.

allergies *are* far more common in developed countries than those that are not. There are a lot of people I know who've moved to the US and whose children have loads of allergies (horribly restricted) while the nephews and neices who stayed behind don't.

It could be worms, but it is important to remember that more sanitary conditions are one of absurdly large number of changes that happen when a society gets a big helping of western culture. There is a lot of co-variation going on. As the overly repeated mantra goes, correlation does not imply causation.

That said, I do think that this is promising and well worth the study. If it is true, it could lead to some interesting methods of treatment Personally, I would prefer not to have the symptoms of hook worms just to eliminate my allergies, but imagine if you could mimic the immune response through some other way, like through harmless parasites or even drug manipulation..